Hydroforming using a platinum on alumina base catalyst



May 16, 1961 R. M. BUTLER ETAL HYDROFORMING USING A PLATINUM ON ALUMINA BASE CATALYST Filed Jan. 12, 1959 BUTANES 23 22 BUTANE I4 l5\' MAKE GAS 4\ HYDRQGEN g A a 2| I \I \II U NAPHTHA FEED s REACTOR SEPARATOR DEPROPANIZER DEBUTANIZER- REFORMATE R0 er M. urler g B Inventors John A. Bichord By Attorney United States Patent HYDROFORMING USING A PLATINUM ON ALUMINA BASE CATALYST search and Engineering Company, a corporation of Delaware Filed Jan. 12, 1959, Ser. No. 786,268 4 Claims. (Cl. 208-139) The present invention relates to improvements in the reforming of hydrocarbon fractions boiling in the motor gasoline or naphtha boiling range. More particularly, the present invention relates to improvements in hydroforming using a platinum on alumina base catalyst.

Hydroforming is a process used to increase the octane number of hydrocarbon fractions boiling in the naphtha boiling range. It has been defined as an operation conducted at elevated temperatures and pressures in which the naphtha feed is contacted with a solid catalytic material in the presence of added hydrogen. The process is so operated that there is usually a net production of hydrogen.

At the present time, there are two principal methods of hydroforming. These methods are referred to as fixed bed hydroforming and fluid hydroforming. In the fixed bed method of hydroforming the usual procedure is to pass a naphtha feed mixed with hydrogen-rich gas successively through a bank or group of reactors with reheating of the reaction mixture between each reactor. Such a hydroforming system normally comprises three or four reactors operating in series and the system may be regenerative, semi-regenerative or non-regenerative. The fluid bed method of hydroforming consists of only one reactor zone or vessel and utilizes the fluid solids technique to maintain circulation of the finely divided catalyst particles between the reactor and regenerator. It is to be understood that the present invention may be utilized in either the fixed bed or fluid bed method of hydroforming.

When reforming under normal conditions, coke is formed. The coke produced is both wasteful and harmful in that it reduces the yield of valuable products and becomes deposited on catalyst particles making the catalyst less active and requiring regeneration. In normal hydroforming operations, hydrogen or hydrogen-rich recycle or process gas is added to the reaction to reduce this deposition of coke on the catalyst by saturating the olefins which are formed by the reaction. These hydrogenated olefins are largely gaseous and a considerable loss in liquid yield results when the product is separated from the light gases.

The object of the present invention is to provide an improved method of hydroforming whereby both yield and octane number of the gasoline produced are increased over normal hydroforming under similar conditions. Other objects will be apparent from the detailed specification and claims which follow.

It has now been found that better yields of higher octane gasoline can be produced by passing a naphtha feed over certain platinum on alumina hydroforming catalysts in the presence of isobutane, normal butane or a mixture of isobutane and normal butane which have been added to the reaction. By adding butanes, an alkyl- ICC ation type reaction occurs whereby the butanes react with the olefins formed in the reaction. Instead of light gases being produced by the hydrogenation of these olefins and a loss in yield resulting, the olefins are alkylated by the butanes and liquid yields and product quality are improved.

In the past it has been known to hydroform in the presence of these C -C aliphatic hydrocarbons. This has been disclosed in Us. Pat. No. 2,405,184 and British pat. spec. 775,963. The essence of the present invention rests in hydroforming in the presence of C -C aliphatic hydrocarbons using a platinum on alumina catalyst having a limited chlorine content. By using a platinum on alumina catalyst with a chlorine content of about 0.1-0.5 wt. percent, ususual and unobvious results are obtained as is shown by the examples hereinafter.

The process of the present invention may be more fully understood by referring to the accompanying drawing illustrating diagrammatically a flow plan of one embodiment of the same. It is to be understood that the reactor shown in the accompanying drawing may be either of the fixed bed type or of the moving bed or fluid bed type. It should also be understood that it is within the scope of the present invention to employ a group or bank of fixed bed reactors with furnaces between the reactors for reheating.

Reactor 7 will be referred toas a fixed bed type reactor, but this in no way limits the scope of the invention.

Referring specifically to the drawing, a hydrofined naphtha fraction boiling in the range of to 400 F. is introduced into line 2. Simultaneously with the introduction of the naphtha feed, hydrogen or hydrogenrich recycle gas is introduced into line 2 by means of line 4 and butanes are introduced into line 2 by means of line 5. This mixture passes through line 2 and enters furnace 3 where it is heated to a temperature of about 1000 F.

From furnace 3, the heated mixture passes through line 6 to reactor 7 wherein the heated mixture contacts a fixed bed of platinum on alumina base catalyst contained in the reactor. The temperature, pressure and other operating conditions in reactor 7, which will be hereinafter described, are adjusted to secure a hydroforming operation.

The hydroformed mixture leaves reactor 7 via line 8 and is cooled and partially condensed in cooler 9. From cooler 9, the hydroformate is introduced into separator 11 via line 10 where hydrogen containing gas which passes out the top is separated from the remaining mixture or liquid product. The hydrogen-containing gas passes out of separator 10 through line 12 and is recycled to line 2 by means of line 13, line 4 and recycle pump 14. Excess make gas containing hydrogen is withdrawn through line 15.

The liquid from separator 11 passes through line 16 to depropanizer 17 wherein the propane and lighter material is withdrawn overhead through line 19. The liquid material remaining in depropanizer 17 is passed through line 18 to debutanizer 20. In debutanizer 20, the butanes are separated and recycled if desired to line 2 via lines 21 and "5 and recycle pump 22. Fresh butanes may be added or withdrawn through line 23. The

debutanized liquid product passes from the bottom of debutanizer 20 by way of line 24.

Although butane recycle has been shown, it is to be understood that this is not a necessary feature and the butanes used need not be those separated from the final product.

The conditions necessary for hydroforming are set forth in tabular form below.

The feed stock which is ,used in the present invention is a naphtha fraction boiling in the range of 140 to 400 F. The naphtha fraction may be virgin naphtha, cracked naphtha or paraflinic naphtha. It is usually preferred that the feed stock be hydroformed or at least that the sulfur content of the feed to the platinum hydroformer be kept at a level which does not poison the platinum catalyst.

The catalyst used in this invention is a platinum catalyst supported on an acidic alumina base. The degree of acidity of' the base of this catalyst is equivalent to from to about 0.5 wt. percent chlorine based on the total catalyst composition. A commonly used composition of a catalyst used in normal hydroforming operations is one containing from 0.001 to 2.0 wt. percent platinum, 0.5 to 1.5 Wt. percent chlorine, and the remainder an adsorptive alumina spacing agent or base. This amount of chlorine, 0.5 to 1.5 Wt. percent, is commonly referred to as the cant help it amount because it is the chlorine content resulting from the normal use of chloroplatinic acid in the formation of the catalyst. For the present invention a catalyst such as this which has been used in a hydroforming operation and has thereby lost some of its chlorine content and now is within the required range of chlorine content is considered excellent for this invention. The catalyst may be made by methods known to the art but when in use the degree of acidity must be limited as just described. The process of the present invention may be more fully understood by the following examples illustrating the same.

Example I A feed consisting of 50% cyclohexane and 50% normal heptane was hydroformed under normal hydroforming conditions using approximately 6500 s.c.f./b. of hydrogen and a spent platinum on alumina hydroforming catalyst containing 0.6 wt. percent platinum, and between 0.6 to 1.0 wt. percent chlorine. The catalyst had been previously used in hydroforming operations and the chlorine content of the catalyst had been reduced to an extent wherein the eifective chlorine content was about 0.3 wt. percent before being used in this experiment.

Butanes equivalent to 3.9 wt. percent of the naphtha feed were produced.

' The above example shows the results of replacing part hydrogen gas with isobutane. The fact that an amount of butanes equivalent to 14 wt. percent of the naphtha feed was consumed and that a very high C yield was obtained would show that an alkylation reaction has occurred. The information obtained for this example shows that a larger liquid yield and higher octane number product can be obtained by the reduction of the hydrogen rate and the addition of isobutane to the hydroformer feed. By the addition of isobutane according to the present invention, a yield of 97.6 wt. percent with a research (clear) octane number of 92.6 has been obtained as compared to a yield of 86.6 Wt. percent and a research (clear) octane number of 84.6 when hydroforming in the conventional manner.

As previously indicated, the aliphatic hydrocarbon used in the present invention may be either normal butane or isobutane. This is shown by the next example.

Example 11 Again the same feed as used in Example I was hydroformed using a 0.6 wt. percent platinum catalyst that originally contained 0.6 wt. percent chlorine which was reduced in chlorine content to an extent wherein the elfective chlorine content was about 0.3 wt. percent and no chlorine treatment was used during the experiment to raise the chlorine level.

Pressures, p.s.i.g. Run No. 05+Yi8ld, Res. O.N.,

- I I I I LV Percent Clear Total H; 104 not It will be noted that the hydrogen partial pressures were equivalent during all these runs and that approximately the same advantage was obtained for both iso and normal butane.

Example III A hydrocarbon feed containing 50% cyclohexane and 50% normal heptane was again hydroformed under normal hydroforming conditions of 900 F. and 450 p.s.i.g. The catalyst in each case was 0.6 wt. percent platinum on an alumina base but in each case the state of the catalyst was different. The results obtained in Exampic I, using the spent platinum on alumina catalyst (designated as catalyst A having an effective chlorine content of 0.3 wt. percent) were compared with both a fresh catalyst and chlorine treated catalyst which contained a higher chlorine content than the catalyst of Example I.

Catalyst B was a fresh platinum on alumina catalyst containing about 0.6 wt. percent chlorine and catalyst C was a catalyst which had been regenerated and chlorine treated 3 times in the previous hours of operation and now had a chlorine content of approximately 1-2 From this comparison we can again see the unexpected and unobvious results gained by using the catalyst of limited chlorine content. By using catalyst A, an increase in the alkylation reaction is obtained as shown by the increase in the amount ofbutanes consumed. By using catalyst A, a yield of from 10 to 16 Wt. percent higher than the yields from the other catalysts examined was obtained and a research (clear) octane number comparable to that obtained with fresh catalyst B and vastly superior to that of catalyst C is obtained by utilization of the present invention.

Chlorine content on platinum catalyst when used in hydroforming has two effects. One eifect is good in that the activity of the catalyst is increased while the second effect is bad in that the deactivation rate of the catalyst is increased. This is shown by Example IV.

Example IV The 0.6 wt. percent platinum catalyst used in this experiment were so pretreated as to contain different amounts of chlorine. The catalyst of run 1 was pretreated with 2 wt. percent chlorine and therefore had the most chlorine present at the time of the run. The catalysts of runs 2 and 3 were steam treated in such a manner as to remove a large portion of the chlorine from the catalyst of run 2 and all of the chlorine from the catalyst of run 3. The feed was a hydrofined naphtha boiling between 40 and 330 F. The feed rate was 1.5 w./w./hr. and the hydrogen recycle rate was 6000 s.c.f./b.

Run No 1 2 3 Catalyst Pretreat Average Activity Temperature, F--."

Yield, LV Per cent at 99 Research Octane N 0.

Relative Deactivatlon Rate.

Mild Steam Treat.

Severe Steam Treat.

2 wt. Percent Low.

By reducing the chlorine content of the catalyst as is disclosed in this invention an added advantage of decreasing the catalyst activation rate and therefore allowing higher temperatures with less adverse effects is possible as shown by the last example.

Example V The feed and catalyst used in the experiment is the same as that used in Examples 1 and 2. The chlorine content of the catalyst has been reduced to an effective content of about 0.3 wt. percent and no chlorine treatment of the catalyst was made during the experiment. The pressure was maintained at 450 psi.

From this experiment it can be seen that at high temperatures of 900 F. and above both the yield of valuable product and the octane number are increased.

In brief, this invention is an improved method of hydroforming in the presence of isobutzanes. The improvement is in the control of the chlorine content of the platinum on alumina catalyst. By limiting this chlorine content unexpected and unobvious results consisting of better yields, higher octane product, and less catalyst deactivation of higher temperature are obtained.

It is understood that the invention is not limited to the specific examples which have been offered merely as illustrations and that modifications may be made without departing from the spirit of the invention.

What is claimed is:

1. In a process of hydroforming naphtha hydrocarbons boiling between about and 400 F. in the presence of a platinum on alumina catalyst and hydrogen at a hydroforming reaction temperature in the range of 850 to 1100 F. and under a total pressure in the range of about 300 to 825 p.s.i.g., the improvement which comprises maintaining a chlorine content in said catalyst of about 0.3 wt. percent and supplying enough added butane to replace hydrogen so that the hydrogen partial pressure is in the range of about to 355 psi. with a higher hydrocarbon partial pressure of the butane plus said naphtha hydrocarbons subjected to the hydroforming to increase reaction of the butane and thereby give an increased liquid product yield.

2. In the process defined by claim 1, the ratio of hydrogen partial pressure to butane partial pressure is in the range of about 164:212 to 355:303.

3. In the process defined by claim 1, in which the added butane is selected from the group consisting of normal butane, isobutane and a mixture of said butanes.

4. In the process defined by claim 1, in which the added butane is in at least about equal volume with the hydrogen to effect formation of olefins and alkylation of said olefins by the butane in the hydroforming of the naphtha hydrocarbons.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A PROCESS OF HYDROFORMING NAPHTHA HYDROCARBONS BOILING BETWEEN ABOUT 140* AND 400*F. IN THE PRESENCE OF A PLATINUM OF ALUMINA CATALYST AND HYDROGEN AT A HYDROFORMING REACTION TEMPERATURE IN THE RANGE OF 850* TO 1100*F. AND UNDER A TOTAL PRESSURE IN THE RANGE OF ABOUT 300 TO 825 P.S.I.G., THE IMPROVEMENT WHICH COMPRISES MAINTAINING A CHLORINE CONTENT IN SAID CATALYST OF ABOUT 0.3 WT. PERCENT AND SUPPLYING ENOUGH ADDED BUTANE TO REPLACE HYDROGEN SO THAT THE HYDROGEN PARTIAL PRESSURE IS IN THE RANGE OF ABOUT 150 TO 355 P.S.I. WITH A HIGHER HYDROCARBON PARTIAL PRESSURE OF THE BUTANE PLUS SAID NAPHTHA HYDROCARBONS SUBJECTED TO THE HYDROFORMING TO INCREASE REACTION OF THE BUTANE AND THEREBY GIVE AN INCREASED LIQUID PRODUCT YIELD. 